Radio broadcast distributing system



March 19, 1929.

Filed March 15, 1926 2 Sheets-Sheet 1 2.2 a 62 F .2. 0 V z I6 8 252 I zfiza REC.

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RADIO BROADCAST DISTRIBUTING SYSTEM 2 Sheets-Sheet 2 Filed March 15, 192

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PFOGEAM Ween-curs per/cs6 Patented Mar. 19, 1929.

PATENT OFFICE.

UNITED STATES EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TO ED- WARD F. COLLADAY, OF WASHINGTON, DISTRICT 01 COLUMBIA.

RADIO BROADCAST DISTRIBUTING SYSTEM.

Application filed March 15, 1926. Serial No. 94,851.

My invention relates to systems of radio broadcast distribution and has for its object the organization of a system capable of giving service to subscribers in regional groups, which may be related to each other by' a general organization corresponding to the long distance telephone organization.

I attain my object by relating my subscribers in each area to one or more local central oflices, by means of wired circuits, which may conveniently be telephone or electric light circuits. Each subscriber is provided with a standardized form of receiving radiophone, and each central'oflice 5 is also provided with receiving radiophones, but much more elaborate and powerful than those at the subscribers stations. Local service, that is to say,

local broadcasting, may be received lvthe subscriber direct but when he desires any station except those that are listed as local, he may secure connection through his wires to the central olfice radio receiving set. The subscribers instrument may conveniently be a single tube regenerative set with common battery connections, taking all its current supply over the wired circuit. The central ofiice radio sets may conveniently be superheterodynes, or the equivalent thereof, capable of receiving from distant stations and transforming the carrier wave length so as to relay or retransmit the original modulations over the wires on a long carrier wave, preferabl at superaudio frequency, 5 such as 30 to 60 e. per second.

The advantages of this arrangement will be apparent on brief consideration. A single tube set is usually sufiicient to give excellent results with local broadcasting, and

by using a dynamic receiver, it is even possible to operate therewith a moderately loud table talker or loud speaker. For distance work, the antenna or equivalent wave collector is unnecessary, and the input side is connected through a tuned coupler to the wire circuit. The same tube detector in the subscribers set then receives the distant signals on long waves, without the necessity of elaborate tuning on the part of-the subscriber.

This application is a continuation in part of my prior application Serial No. 6,071, filed January 21, 1925, patented March 16, 1926, No. 1,577,109.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a diagram of a subscribers station.

Fig. 2 is a connected diagram of the central oflice end of the subscribers Wired line circuit, showing terminal devices and switching means therefor.

Fig. 3 is a diagram showing a subscribers radio receiver of the local battery type adapted to be substituted for that of Fig. 1.

Fig. 4 is a diagram showing the invention applied to a power line network.

Referring to the drawings, Figs. 1 and 2 are to be read together, the dotted lines aa and bb in Figs. 1 and 2 being spaced apart to indicate distance between the subscribers station and the central oflice.

Fig. 1 represents a subscribers instrument. 1 is a detector tube with the usual filament 2, grid 3 and plate 4. 5 and 6 are rheostats, 7 is a choke coil, 8 is a telephone transmitter of standard type adapted to be bridged across the line wires 9 and 10 by the push button or key 11, which however, opens as soon as pressure is removed from it. 12 is the subscribers headphone, 13 is a loop antenna for local receiving, 14 is a tickler loop or regenerative coil, 15 is the usual tuning condenser across the loop, 1617 is a coupler for connecting the instrument to line for long distance receiving. 18 and 19 are tuning condensers for the long distance circuit, 20 and 21 are radio frequency choke coils included in the branch of the ordinary telephone set 22, and 23 is a gang switc adapted to connect the instrument for either long distance or local receiving to the telephone line wires 9-10, or to disconnect it entirely therefrom at will. There are no batteries at the subscribers station, all energy for all purposes being supplied over the metallic circuit 9-,10, from the telephone exchange central office shown in Fig. 2.

Fig. 2 shows one telephone line 910 with the switching terminals in the form of sprinlgjacks J--J', a line relay L, battery B, cut-o relay C, a signal lamp S. These elements of the line, as shown, are alliold and well understood, and for the purpose of connecting this line with others for telephonic use, standard Western Electric No. 1 switchboard cord circuits are supposed to be employed, which however, are not shown separately herein. The line 9-10, and any number of other lines assumed to be taking radio service, must be supplied with centralized current during operation of their radiophones without keeping their signal lamps S burning, this applying to both local and long distance service. For local receiving no other connection is required at the central office, but for receiving from distant stations, the subscribers line is connected at the central ofiice through an amplifier or relay device 37, individual to the line, to a receiving instrument 60, the amplifier circuit of the amplifier 37 being supplied from a battery B controlled through a switch 30. The connection of the line with the set 60 is shown in Fig. 2 as established by means of keys K-K which may be left normally closed, because radio frequency condensers are included in the circuits. In such case the subscriber can secure long distance service by merely turning his own switch into the proper position and signaling the operator at the central ofiice to close his filament switch 30 which signal is given by operation of the key 11 to flash his line lamp. However, this permanent connection would give him access to only one central receiver, and he would be limited to the program received from stations selected by the central office operators. In order to give him a wider choice, I have indicated also interchangeable switching means consisting of multiple keys K 3 for connection with busses 26-27 and 2829, which typify any desired number of program busses of different receiving instruments, the different keys K, K etc. being actuated by an operator in response to request made telephonically over the line wire.

The use of the manually operated switching ke s K, K, etc. is here shown mainly for the sa e of simplicity of disclosure, it being understood that any known or other suitable switching means may be used instead, such for example as the automatic switching means shown and described in my copending application Serial No. 7 54,406, filed December e, 1924.

The receiver or receivers such as 60 (Fig. 2) at the central station may be of any known or other suitable form capable of receiving radio broadcast matter and relaying it onto the busses 2425 with amplifier or increased power and in the form of a modulated carrier wave of a frequency suitable for line transmission. The preferred form is that of a superheterod ne receiver such as ceiver and relay apparatus of the superheterodyne type the connection would be made by inductively coupling the output circuit of an oscillator 61 with the input or detector circuit of the superheterodyne in place of the antenna circuit, as will be well understood by those skilled in the art; and as is shown in the prior patent above referred to.

For simplicity in operation it is preferable to maintain the carrier current on the wires at a substantially constant frequency, the subscriber sharpening up the tuning, if necessary, by adjustment of the variable condensers 1819, (Fig. 1).

Where the subscribers apparatus of Fig. 3 is substituted for that of Fig. 1, the operation is the same as that of Fig. 1, except that the supply of current for the filament and plate circuit or circuit-s is furnished from a local source. In other words, the subscnber's. radio receiver 63 may be of any known or other type capable of receiving bbth long and short waves, the coupling to the line 9-10 being effected through the same tuned coupling connection 16-17 and 18-19, by throwing the switch 64, corresponding to the switch 23 of Fig. 1, from the antenna and ground connection, to the tuned coupler connection, thus making the necessary change of tuning automatic in response to the" switching off of the input circuit of the receiver from the antenna to the line.

In Fig. 4, the system is shown applied to a power line network instead of a telephone sysem. In this arrangement the subscribers receiving set and the broadcast transmitting apparatus are substantially the same with certain changes in the manner of connection with the networks required by the necessity of protecting one system from the other and properly filtering the different kinds of current. Here the conductors 910 represent an electric light or power supply line supplying various current consuming devices such as the lamps 700, and forming part of a current supply network fed from the power busses 71-72 at the power station which is that portion of the system indicated below the dotted lines 0-11 and b-b, the space between these dotted lines representing the indefinite distance between the subscribers station and the main station. At the main station, the power busses are supplied with the broadcast matter from the source 60 in the same manner as in the system of Figs. 1 and 2, except that here the am lifier 37 is not individual to one subscriber but supplies the busses 71-72 common to a large number of subscribers stations, and is representative of an amplifier unit of one or more tubes according to the amount of amplification required. Suitable protective devices may be included in the connection between the power source 73 and the bus 71-72 to prevent unnecessary leakage of the signal energy through the generator and its accessories. At the subscribers station the connections of the broadcast receiving set are the same as those of Fig. 1 except that the supply of operating energy therefor is derived from the electric light line 9-10 through a transformer device 74 of any known or other suitable form such as a so called battery eliminator. Where the tuned coupling circuit 17-19 is insufficient to protect the set from unavoidable power line noises such as A. C. hum in the case of alternating current lines, or ripple in the case of direct current lines, a suitable filter device 75 may be inserted in the connection with the line.

The operation of the system of Fig. 4 is the same as that of Figs. 1 and 2 except that the subscriber desiring line broadcast service may receive the same by simply moving the switch 23 down into the line' service position without requiring special or individual service at the main station. The switch 30 at the central or transmitting office will obviously be left closed during program hours.

What I claim is:

\1. In a system of broadcast distribution, a central station and subscribers stations connected thereto by wires, a radio telephone receiving set at each subscribers station and an antenna therefor, means at the central station for supplying carrier current to the said wires, means for operatively connecting the input circuit of the subscribers radio receiving set with either the antenna or the wire and means operable upon the switching of said input. circuit from the antenna to the wire to automatically change the tuning of said receiving set from short wave lengths to long wave lengths.

2. In a system of radio broadcast distribution, a central station and subscribers sta-l tions connected thereto by wires, a radio receiving set at each subscribers station and an antenna therefor, means at the central station for supplying carrier current to said wires, means for connecting the subscribers receiving set with either the antenna or the wire, and in the latter case means for simultaneously adapting the said set to receive long waves over the wires.

3. In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by wires, a radio receiving set at each subscribers station and an antenna therefor, means at the central station for electrically transmitting broadcast matter over said wires, means for connecting the subscribers receiving set with either the antenna or the wire, and in the latter case means for simultaneously adapting the said set to receive long waves over i the wires.

4. In a system of radio broadcast distribution, a central station and subscribers stations connected thereto by wires, a radio receiving set at each subscribers station and an antenna therefor, means at the central station for transmitting a low frequency carrier current over the wires, a highfrequency receiving circuit and a low frequency receiving circuit at each subscribers station tuned to frequencies of a high order and to said low frequenc carrier current, respectively, means at each subscribers station for connecting the input side of the said radio receiving set to either the antenna circuit or through the low frequency tuned receiving circuit to the wire, and means to simultaneously connect either the high frequency or the low frequency receiving circuit, according to the medium employed for receiving.

5. In a system of broadcast distribution, an electrical distributing network, subscribers stations connected with said network, a radio receiving set at each subscribers station and an antenna therefor, means for supplying carrier current to the network, and means for o eratively connecting. the input circuit oi said subscribers radio receiving set with either the antenna or the network, and means for simulta- 95 neously adapting the said set to receive either short or long waves according to the medium with which it is connected.

6. In a system of broadcast distribution, an electrical distributing network, sub- 100 scribers stations connected with said network, a radio receiving set at each subscribers station and an antenna therefor, meahs for supplying carrier current to the network, and means for'operatively connecting the input circuit of said subscribers radio receiving set with either the antenna or the network, together with means operable upon the switching of said input circuit from the antenna. to the network to no automatically change the tuning of said receiving set from short wave lengths to long 1 wave lengths. 7. In a system of broadcast distribution, an electrical distributing network, subscribers stations connected with said network, a radio receiving set at each sub scribers station and an antenna therefor,

means for supplying carrier current to the network, means for operatively connecting the input circuit of said subscribersradio receiving set with either the antenna or the network, and means for simultaneously adapting said input circuit to receive either short waves or long waves, together with means'for supplying energy over the network for operating said subscribers receiving set.

8. In a system of broadcast distribution, an electrical distributing network, subscribers stations connected with said network, a radio receiving set at each subscribers station and an antenna therefor, means for supplying carrier current to the network, means for operatively connecting the inputcircuit of said subscribers radio receiving set with either the antenna or the network, and means for simultaneously adapting said input circuit to receive either short waves or long waves, together with 10 In testimony whereof I hereuntoifiix my 15 signature.

EDWARD E. CLEMENT. 

